U.S. patent application number 10/912564 was filed with the patent office on 2005-04-14 for process of preparing regioregular polymers.
Invention is credited to Falk, Birgit, Giles, Mark, Koller, Guntram, McCulloch, Iain, Weller, Clarissa.
Application Number | 20050080219 10/912564 |
Document ID | / |
Family ID | 34137567 |
Filed Date | 2005-04-14 |
United States Patent
Application |
20050080219 |
Kind Code |
A1 |
Koller, Guntram ; et
al. |
April 14, 2005 |
Process of preparing regioregular polymers
Abstract
The invention relates to a process of preparing regioregular
polymers, in particular head-to-tail (HT) poly-(3-substituted)
thiophenes with high regioregularity, to novel polymers prepared by
this process, to the use of the novel polymers as semiconductors or
charge transport materials in optical, electrooptical or electronic
devices including field effect transistors (FETs),
electroluminescent, photovoltaic and sensor devices, to FETs and
other semiconducting components or materials comprising the novel
polymers, to a process of endcapping polymers and to endcapped
polymers obtained thereof and their use in the above devices.
Inventors: |
Koller, Guntram; (Darmstadt,
DE) ; Falk, Birgit; (Riedstadt, DE) ; Weller,
Clarissa; (Darmstadt, DE) ; Giles, Mark;
(Bitterne Park, DE) ; McCulloch, Iain; (Chandlers
Ford, GB) |
Correspondence
Address: |
MILLEN, WHITE, ZELANO & BRANIGAN, P.C.
2200 CLARENDON BLVD.
SUITE 1400
ARLINGTON
VA
22201
US
|
Family ID: |
34137567 |
Appl. No.: |
10/912564 |
Filed: |
August 6, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60493451 |
Aug 8, 2003 |
|
|
|
Current U.S.
Class: |
528/73 |
Current CPC
Class: |
Y02E 10/549 20130101;
H05B 33/14 20130101; C09K 11/06 20130101; C08G 61/126 20130101;
C09K 2211/1458 20130101; H01L 51/0036 20130101 |
Class at
Publication: |
528/073 |
International
Class: |
C08G 018/28 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 6, 2003 |
EP |
03017920.4 |
Claims
1. Process of preparing a regioregular poly(3-substituted
thiophene) having a regioregularity of .gtoreq.95% head-to-tail
(HT) couplings, by providing a 3-substituted thiophene having
chloro and/or bromo groups in 2- and 5-position, wherein the
substituent in 3-position is an organic group which when it is
unsubstituted and unmodified straight chained or branched alkyl has
5 or more C-atoms, reacting said thiophene with magnesium in a
solvent comprising a linear ether or a mixture of linear ethers to
form a regiochemical Grignard intermediate or a mixture of
regiochemical Grignard intermediates, and polymerising said
Grignard intermediate by adding a suitable catalyst.
2. Process according to claim 1, by a) dissolving the 3-substituted
thiophene in a solvent or a mixture of solvents, b) adding
magnesium in an at least molar amount of the thiophene to the
solution, or adding the solution to said magnesium, wherein said
magnesium reacts with said thiophene to form a regiochemical
Grignard intermediate or a mixture of regiochemical Grignard
intermediates, c) optionally removing the unreacted magnesium from
the reaction mixture, d) adding a catalyst to the reaction mixture,
or adding the reaction mixture to a catalyst, and optionally
agitating the mixture, to form a polymer, and e) recovering the
polymer from the mixture.
3. Process according to claim 1, characterized in that the
3-substituted thiophene is a 3-substituted
2,5-dibromo-thiophene.
4. Process according to claim 1, characterized in that the
poly(3-substituted thiophene) has a regioregularity of
.gtoreq.98%.
5. Process according to claim 1, characterized in that the solvent
is selected from diethyl ether, di-n-butyl ether, di-n-propyl
ether, di-isopropyl ether, ethers with two different alkyl groups,
1,2-dimethyoxyethane or t-butylmethyl ether, or mixtures thereof,
or mixtures of toluene with one or more of the above ethers.
6. Process according to claim 5, characterized in that the solvent
is diethyl ether.
7. Process according to claim 2, characterized in that the
concentration of the thiophene in the solution in step a) is from
40 to 200 grams per litre.
8. Process according to claim 1, characterized in that the amount
of the magnesium is from >1 to 3 times the molar amount of the
thiophene educt.
9. Process according to claim 8, characterized in that the amount
of the magnesium is from 1.02 to 1.20 times the molar amount of the
thiophene educt.
10. Process according to claim 1, characterized in that the
unreacted magnesium is removed from the reaction mixture before
adding the catalyst.
11. Process according to claim 1, characterized in that the
catalyst is a Ni(II) catalyst.
12. Process according to claim 11, characterized in that the
catalyst is selected from Ni(dppp)Cl.sub.2
(1,3-diphenylphosphinopropane nickel(II) chloride) or
Ni(dppe)Cl.sub.2 (1,2-bis(diphenylphosphino)ethane nickel(II)
chloride).
13. Process according to claim 1, characterized in that the
formation of the regiochemical Grignard intermediate and the
polymerisation (steps a) and d)) are carried out at a temperature
from room temperature to reflux temperature.
14. Process according to claim 13, characterized in that the
formation of the regiochemical Grignard intermediate and the
polymerisation (steps a) and d)) are carried out at reflux
temperature.
15. Process according to claim 1, characterized in that the polymer
is purified after being recovered from the reaction mixture.
16. Process according to claim 1, characterized in that one or more
of the terminal groups of the polymer are chemically modified
(`endcapped`).
17. Process according to claim 1, characterized in that the polymer
is selected of formula I 11wherein n is an integer>1 and R.sup.1
is a group that does not react with magnesium under the conditions
of the process according to any of the preceding or following
claims.
18. Process according to claim 1, characterized in that the
3-substituted thiophene is selected of formula II 12wherein R.sup.1
has the meaning of claim 17, and X.sup.1 and X.sup.2 are
independently of each other Br or Cl.
19. Process according to 17, characterized in that R.sup.1 is
straight chain, branched or cyclic alkyl with 1 or more C-atoms,
which may be unsubstituted, mono- or poly-substituted by F, Cl, Br,
I or CN, it being also possible for one or more non-adjacent
CH.sub.2 groups to be replaced, in each case independently from one
another, by --O--, --S--, --NH--, --NR.sup.0--,
--SiR.sup.0R.sup.00--, --CO--, --COO--, --OCO--, --OCO--O--,
--SO.sub.2--, --S--CO--, --CO--S--, --CY.sup.1.dbd.CY.sup.2-- or
--C.ident.C-- in such a manner that O and/or S atoms are not linked
directly to one another, optionally substituted aryl or heteroaryl,
or P-Sp, with R.sup.0 and R.sup.00 being independently of each
other H or alkyl with 1 to 12 C-atoms, Y.sup.1 and Y.sup.2 being
independently of each other H, F, Cl or CN, P being a polymerisable
or reactive group which is optionally protected, and Sp being a
spacer group or a single bond.
20. Process according to claim 19, characterized in that R.sup.1 is
selected from C.sub.1-C.sub.20-alkyl that is optionally substituted
with one or more fluorine atoms, C.sub.1-C.sub.20-alkenyl,
C.sub.1-C.sub.20-alkynyl, C.sub.1-C.sub.20-alkoxy,
C.sub.1-C.sub.20-thioalkyl, C.sub.1-C.sub.20-silyl,
C.sub.1-C.sub.20-ester, C.sub.1-C.sub.20-amino,
C.sub.1-C.sub.20-fluoroal- kyl.
21. Process according to claim 20, characterized in that R.sup.1 is
selected from straight-chain or branched pentyl, hexyl, heptyl,
octyl, nonyl, decyl, undecyl or dodecyl.
22. Process according to claim 21, characterized in that R.sup.1 is
n-hexyl.
23. Process according to claim 17, characterized in that X.sup.1
and X.sup.2 are Br.
24. Process according to claim 17, characterized in that n is an
integer from 50 to 1,000.
25. Process according to claim 1, characterized in that the polymer
is selected of formula I1 13wherein n is an integer>1 and
R.sup.1 is a group that does not react with magnesium under the
conditions of the process according to any of the preceding or
following claims and X.sup.1 and X.sup.2 are independently of each
other Br or Cl.
26. Process according to claim 16, characterized in that the
polymer after endcapping is of formula I2 14wherein n is an
integer>1 and R.sup.1 is a group that does not react with
magnesium under the conditions of the process according to any of
the preceding or following claims. X.sup.11 and X.sup.22 are
independently of each other H, halogen, Sn(R.sup.0).sub.3 or
straight chain, branched or cyclic alkyl with 1 to 20 C-atoms,
which may be unsubstituted, mono- or poly-substituted by F, Cl, Br,
I, --CN and/or --OH, it being also possible for one or more
non-adjacent CH.sub.2 groups to be replaced, in each case
independently from one another, by --O--, --S--, --NH--,
--NR.sup.0--, --SiR.sup.0R.sup.00--, --CO--, --COO--, --OCO--,
--OCO--O--, --S--CO--, --CO--S--, --CY.sup.1.dbd.CY.sup.2-- or
--C.ident.C-- in such a manner that O and/or S atoms are not linked
directly to one another, optionally substituted aryl or heteroaryl,
or P-Sp, R.sup.0 and R.sup.00 are independently of each other H or
alkyl with 1 to 12 C-atoms, and Y.sup.1 and Y.sup.2 are
independently of each other H, F, Cl or CN.
27. Process according to claim 26, characterized in that X.sup.11
and X.sup.22 are independently of each other alkyl that is
optionally substituted with one or more fluorine atoms, alkenyl,
alkenyl, alkoxy, thioalkyl, silyl, ester, amino or fluoroalkyl, all
of these groups being straight-chain or branched and having 1 to 20
C atoms, or optionally substituted aryl or heteroaryl, or P-Sp as
defined in claim 19.
28. Process according to claim 27, characterized in that X.sup.11
and X.sup.22 denote straight-chain or branched alkyl with 1 to 6 C
atoms.
29. Process according to claim 26, characterized in that one or
both of X.sup.11 and X.sup.22 denote a reactive group or a
protected reactive group.
30. Process according to claim 29, characterized in that the
polymer of formula I2 is further reacted via end group X.sup.11
and/or X.sup.22 with the same or a different polymer of formula I2,
or with another polymer, to form a block copolymer.
31. Polymer or copolymer obtained by a process according to claim
1.
32. Poly-3-substituted thiophene for use as semiconducting
component in an electrical device, a field effect transistor, OLED,
photovoltaic cell or sensor, wherein the terminal groups are
chemically modified (`endcapped polymer`).
33. Poly-3-substituted thiophene according to claim 32,
characterized in that it is endcapped with H or alkyl groups.
34. Polymer according to claim 32, characterized in that it has
improved oxidative stability and/or improved charge carrier
properties.
35. Process of chemically modifying (`endcapping`) the terminal
group of a poly-3-substituted thiophene, during or after
polymerisation, for use as semiconducting component in an
electrical device, field effect transistor, OLED, photovoltaic cell
or sensor.
36. Process of preparing a block copolymer from an endcapped
polymer according to claim 32, wherein one or both of the endgroups
have been modified into a reactive or protected reactive group, by
reacting said polymer via one or both of said reactive or protected
reactive groups with another monomer or polymer.
37. Use of a polymer according to claim 31 as semiconductor or
charge transport material, in particular in optical, electrooptical
or electronic devices, like for example in field effect transistors
(FET) as components of integrated circuitry, as thin film
transistors in flat panel display applications or for Radio
Frequency Identification (RFID) tags, or in semiconducting
components for organic light emitting diode (OLED) applications
such as electroluminescent displays or backlights of e.g. liquid
crystal displays (LCD), for photovoltaic or sensor devices, as
electrode materials in batteries, as photoconductors, for
electrophotographic applications like electrophotographic recording
or for detecting and discriminating DNA sequences.
38. Use of a polymer according to claim 31 as electroluminescent
material, in photovoltaic or sensor devices, as electrode materials
in batteries, as photoconductors, for electrophotographic
applications or electrophotographic recording.
39. Semiconductor or charge transport material, component or device
comprising one or more polymers according to claim 31.
40. Optical, electrooptical or electronic device, FET, integrated
circuit (IC), TFT or OLED comprising a semiconducting or charge
transport material, component or device according to claim 39.
41. TFT or TFT array for flat panel displays, radio frequency
identification (RFID) tag, electroluminescent display or backlight
comprising a semiconducting or charge transport material, component
or device or a FET, IC, TFT or OLED according to claim 39.
42. Security marking or device comprising a FET or an RFID tag
according to claim 41.
43. Polymer according to claim 31 which is oxidatively or
reductively doped to form conducting ionic species.
44. Charge injection layer, planarising layer, antistatic film or
conducting substrate or pattern for electronic applications or flat
panel displays, comprising a polymer according to claim 43.
Description
[0001] This application claims the benefit of the filing date of
U.S. Provisional Application Ser. No. 60/493,451 filed Aug. 8, 2003
which is incorporated by reference herein.
FIELD OF INVENTION
[0002] The invention relates to a process of preparing regioregular
polymers, in particular head-to-tail (HT) poly-(3-substituted)
thiophenes with high regioregularity, and to novel polymers
prepared by this process. The invention further relates to the use
of the novel polymers as semiconductors or charge transport
materials in optical, electrooptical or electronic devices
including field effect transistors (FETs), electroluminescent,
photovoltaic and sensor devices. The invention further relates to
FETs and other semiconducting components or materials comprising
the novel polymers. The invention further relates to a process of
endcapping polymers, to polymers obtained by this process, and to
their use in the above devices.
BACKGROUND AND PRIOR ART
[0003] Organic materials have recently shown promise as the active
layer in organic based thin film transistors and organic field
effect transistors (OFETs) [see H. E. Katz, Z. Bao and S. L. Gilat,
Acc. Chem. Res., 2001, 34, 5, 359]. Such devices have potential
applications in smart cards, security tags and the switching
element in flat panel displays. Organic materials are envisaged to
have substantial cost advantages over their silicon analogues if
they can be deposited from solution, as this enables a fast,
large-area fabrication route.
[0004] The performance of the device is principally based upon the
charge carrier mobility of the semiconducting material and the
current on/off ratio, so the ideal semiconductor should have a low
conductivity in the off state, combined with a high charge carrier
mobility (>1.times.10.sup.-3 cm.sup.2V.sup.-1 s.sup.-1). In
addition, it is important that the semiconducting material is
relatively stable to oxidation i.e. it has a high ionisation
potential, as oxidation leads to reduced device performance.
[0005] There is a need for an improved method of preparing
polymers, particularly poly-(3-substituted) thiophenes with high
regioregularity, high molecular weight, high purity and high yields
in an economical, effective and environmentally beneficial way,
which is especially suitable for industrial large scale
production.
[0006] It was an aim of the present invention to provide an
improved process for preparing polymers with these advantages, but
not having the drawbacks of prior art methods mentioned above.
[0007] Other aims of the present invention are immediately evident
to the person skilled in the art from the following detailed
description.
[0008] The inventors of the present invention have found that these
aims can be achieved, and the above problems be solved, by
providing a process of preparing polymers, in particular
poly-(3-substituted) thiophenes according to the present invention
as described below. According to this process, a 3-substituted
thiophene monomer with at least two groups, wherein these groups
are leaving groups that are capable of reacting with magnesium, is
reacted with magnesium in a suitable solvent to form an
intermediate, which is then polymerized in the presence of a
suitable catalyst. It was surprisingly found that, by chosing
appropriate reagents and reaction conditions, it is possible to
obtain polymers, in particular poly-(3-substituted) thiophenes,
with high regioregularity, high molecular weight and high purity in
good yields and avoiding large amounts of hazardous by-products
that need to be eliminated.
[0009] The polymers prepared by the process according to the
present invention are especially useful as charge transport
materials for semiconductor or light-emitting materials, components
or devices. The above described routes of preparing polymers
usually give a polymer that is terminated by reactive groups such
as halogens, organometallic species such as boronate esters or
trialkyl tins, or very reactive groups such as organo-magnesium or
organo-zincs, which will be quenched under standard work up
procedures. However, these groups have a disadvantageous effect on
the electrical properties of the polymer; for example in
semiconducting applications they can trap charges and thus reduce
the charge carrier mobility of the polymer. It is therefore a
further aim of this invention to further improve the electrical
properties of the polymers obtained by the inventive process and
also by the prior art methods as described above. The inventors
have found that this aim can be achieved by chemical modification
(`endcapping`) of the polymers as described above and below. Thus,
replacing the end groups of the polymers for example with alkyl
groups or hydrogen can give poly(3-alkylthiophenes) with improved
electrical properties. Another aspect of the invention therefore
relates to a process of endcapping polymers, in particular
regioregular poly (3-alkyl thiophenes) and to polymers obtained by
this process.
SUMMARY OF THE INVENTION
[0010] The invention relates to a process of preparing a polymer by
providing a thiophene having at least two groups that are capable
of reacting with magnesium, reacting said thiophene with magnesium
to form a regiochemical Grignard intermediate or a mixture of
regiochemical Grignard intermediates, and polymerising said
Grignard intermediate by adding a suitable catalyst.
[0011] The invention further relates to a process as described
above and below, wherein the thiophene is a 3-substituted soluble
thiophene having groups that are capable of reacting with magnesium
in 2- and 5-position.
[0012] The invention further relates to a process as described
above and below, wherein the polymer is a regioregular head-to-tail
(HT) polymer having a regioregularity of .gtoreq.90%, preferably
.gtoreq.95%, very preferably .gtoreq.98%.
[0013] The invention further relates to a process as described
above and below, by
[0014] a) dissolving a thiophene having two groups that are capable
of reacting with magnesium in a solvent or a mixture of
solvents,
[0015] b) adding magnesium in an at least molar amount of the
thiophene to the solution, or adding the solution to said
magnesium, wherein said magnesium reacts with the thiophene to form
a regiochemical Grignard intermediate or a mixture of regiochemical
Grignard intermediates,
[0016] c) optionally removing the unreacted magnesium from the
reaction mixture,
[0017] d) adding a catalyst to the reaction mixture, or adding the
reaction mixture to a catalyst, and optionally agitating the
resulting mixture, to form a polymer, and
[0018] e) recovering the polymer from the mixture.
[0019] The invention further relates to novel polymers, in
particular novel poly-3-substituted thiophenes, obtainable or
obtained by a process as described above and below.
[0020] The invention further relates to polymers, in particular
poly-3-substituted thiophenes, preferably with high regioregularity
preferably obtained from the process as described above and below,
wherein one or more of the terminal groups are chemically modified
(`endcapped`), especially for use a semiconductors. The invention
further relates to a process of chemically modifying the terminal
group of a polymer, in particular of a poly-3-substituted
thiophene, during or after polymerisation (`endcapping`).
[0021] The invention further relates to a semiconductor or charge
transport material, component or device comprising one or more
polymers as described above and below.
[0022] The invention further relates to the use of polymers
according to the invention as semiconductors or charge transport
materials, in particular in optical, electrooptical or electronic
devices, like for example in field effect transistors (FET) as
components of integrated circuitry, as thin film transistors in
flat panel display applications or for Radio Frequency
Identification (RFID) tags, or in semiconducting components for
organic light emitting diode (OLED) applications such as
electroluminescent displays or backlights of e.g. liquid crystal
displays (LCD), for photovoltaic or sensor devices, as electrode
materials in batteries, as photoconductors and for
electrophotographic applications like electrophotographic
recording.
[0023] The invention further relates to the use of the polymers
according to the present invention as electroluminescent materials,
in photovoltaic or sensor devices, as electrode materials in
batteries, as photoconductors, for electrophotographic applications
or electrophotographic recording or for detecting and
discriminating DNA sequences.
[0024] The invention further relates to an optical, electrooptical
or electronic device, FET, integrated circuit (IC), TFT or OLED
comprising a semiconducting or charge transport material, component
or device according to the invention.
[0025] The invention further relates to a TFT or TFT array for flat
panel displays, radio frequency identification (RFID) tag,
electroluminescent display or backlight comprising a semiconducting
or charge transport material, component or device or a FET, IC, TFT
or OLED according to the invention.
[0026] The invention further relates to a security marking or
device comprising a FET or an RFID tag according to the
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIG. 1 shows forward transfer characteristics for polymers
With different endgroups according to example 1 and 2 of the
present invention.
[0028] FIG. 2 shows repeated forward transfer scans for polymers
with different endgroups according to example 1 and 2 of the
present invention.
[0029] FIG. 3 shows transistor output characteristics at low
V.sub.sd for polymers with different endgroups according to example
1 and 2 of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0030] The polymers prepared by the process according to the
present invention are preferably selected of formula I 1
[0031] wherein n is an integer>1 and R.sup.1 is a group that
does not react with magnesium under the conditions as described for
the process according to the present invention above and below.
Preferably R.sup.1 is an organic group which when it is
unsubstituted and unmodified straight chained or branched alkyl has
5 or more C-atoms. Very preferably R.sup.1 is an organic group
having 5 or more C-atoms.
[0032] The thiophene used as educt in the process according to the
present invention is preferably selected of formula II 2
[0033] wherein R.sup.1 has the meaning given in formula I and
X.sup.1 and X.sup.2 are independently of each other a group that is
capable of reacting with magnesium. Especially preferably X.sup.1
and X.sup.2 are Cl and/or Br, most preferably Br.
[0034] The process according to the present invention offers
significant advantages over the methods disclosed in prior art
especially regarding economical and ecological aspects, whilst
providing polythiophenes in comparable or even better yield and
quality.
[0035] With the process according to the present invention it is
possible to prepare polythiophenes, in particular
HT-poly-(3-substituted) thiophenes with a regioregularity of 90% or
higher in a yield of 50% or higher (related to the thiophene
educt). As mentioned above, these highly regioregular
HT-poly-(3-substituted) thiophenes are particularly suitable for
use as charge-transport or semiconductor material in electronic or
optical devices.
[0036] The regioregular polymers of the present invention thus have
a high number, and do preferably exclusively consist, of HT-linked
repeating units as shown in formula Ia 3
[0037] Furthermore, the costly and difficult preparation of
Grignard reagents like organomagnesium halides is not necessary,
instead magnesium can be used as reagent. Also, the emission of
large amounts of hazardous by-products like methyl bromide can be
avoided.
[0038] The general method of adding magnesium instead of Grignard
reagents like organomagnesium halides has been described in prior
art for the preparation of polythiophenes and
poly-3-alkylthiophenes. However, magnesium is generally not
considered to be highly regioselective in conventional Grignard
reactions. This is supported by the teaching of the prior art
documents mentioned above, which do not report polymers with high
regioregularity.
[0039] The inventors of the present invention have found that
polythiophenes with high regioregularity, high molecular weight and
good processability can be obtained by appropriate selection of the
reaction conditions and the reagents, like the use of linear ethers
as solvents and of thiophene monomers with bromo or chloro groups
in 2/5-position as educts. Also, the use of 3-substituted
thiophenes with organic substituents in 3-position that preferably
have 5, 6 or more C-atoms improves the processability and
solubility of the polythiophene. As a result, during polymerisation
the growing polymer remains longer in solution and a high molecular
weight and good regioregularity can be obtained.
[0040] After polymerisation the polymer is preferably recovered
from the reaction mixture, for example by conventional work-up, and
purified. This can be achieved according to standard methods known
to the expert and described in the literature.
[0041] As a result of the process according to the present
invention, the obtained polythiophenes are usually terminated by
the leaving groups that are capable of reacting with magnesium in 2
and 5-position of the thiophene monomer, or derivatives thereof. In
case thiophene educts of formula II are used, the obtained polymers
correspond to formula I1 4
[0042] wherein n, R.sup.1, X.sup.1 and X.sup.2 have the meanings
given in formula I and II.
[0043] Another object of the present invention is a process of
chemically modifying the reactive terminal groups of a polymer, in
particular a poly-3-substituted thiophene, during or after
polymerisation. This process is hereinafter also referred to as
`endcapping`. Another object of the invention is a polymer, in
particular a poly-3-substituted thiophene, wherein the terminal
groups are chemically modified to replace monomer end groups,
hereinafter also referred to as `endcapped polymer`. Another object
of the invention is the use of an endcapped polymer, in particular
an endcapped poly-3-substituted thiophene, as semiconductor or
charge transport material, in particular for the uses and devices
as described above and below.
[0044] Endcapping of polyalkylthiophene is known in the art and is
described for example by B. M. W. Langeveld-Voss, R. A. J. Janssen
et al., Chem Commun 2000 81-82, and J. Liu., R. S. Loewe and R. D.
McCullough, Macromolecules, 1999, 32 5777-5785, as an aid for
understanding the reaction mechanism (Liu, Janssen) or to enable a
later reaction of the polymer or to encourage binding to a
substrate (Janssen). Furthermore, U.S. Pat. No. 6,602,974 describes
the chemical modification of polyalkylthiophenes by replacing the
terminal halogen groups with H or functional end groups for the
preparation of block copolymers.
[0045] The inventors of the present invention have found that
endcapping can also be used as a suitable method to provide a
polymer with improved electrical properties. For example, by
removing bromine end groups from the polymer chains, a source of
charge carrier trapping is eliminated and higher charge carrier
mobilities can be observed. The main benefit concerns the
improvement in transistor performance stability. The carbon-bromine
bond is susceptible to undergo further reaction in the presence of
charged species, which are present during transistor operation.
These suspected chemical reactions both change the properties of
the semiconducting polymer, as well as release mobile ions, which
lead to transistor hysteresis and threshold voltage drifts.
Endcapping reduces the reactivity of the charged polymer and hence
improves stability.
[0046] Thus, another aspect of the invention relates to a method of
improving the electrical properties, like the charge carrier
mobility, and the processability, of a polymer, in particular of a
polyalkylthiophene, by chemically modifying the endgroups of the
polymer (endcapping) as described above and below. Another aspect
of the invention relates to endcapped polymers and their use as
semiconductors, for example in the applications as described above
and below.
[0047] The process of endcapping by conversion of, for example,
residual halogen end groups into other groups or reactive species
is not limited to polymers obtained by the method of the present
invention. It can also be carried out with other polymers, for
example those obtained by the methods of Rieke, McCullough, Suzuki
or Stille as described above.
[0048] Endcapping can be carried out before or after recovering the
polymer from the polymerisation reaction mixture, before or after
work-up of the polymer or before or after its purification,
depending on which is more suitable and more effective regarding
the material costs, time and reaction conditions involved. For
example, in case expensive co-reactants are used for endcapping it
may be more economical to carry out the endcapping after
purification of the polymer. In case the purification effort is
economically more important than the co-reactants it may be
preferred to carry out the endcapping before purification or even
before recovering the polymer from the polymerisation reaction
mixture.
[0049] Especially preferred are endcapped poly-3-substituted
thiophenes obtained by a Grignard reaction with magnesium according
to the inventive process as described above and below, wherein the
reactive terminal groups of the polymer are chemically modified
during or after polymerisation, or after recovering the polymer
from the mixture, or after purification of the polymer.
[0050] As a result of the process according to the present
invention, at the end of the polymerisation step the end groups
X.sup.1 and X.sup.2 are either a halogen or Grignard group. At this
stage, an aliphatic Grignard reagent RMgX or dialkyl Grignard
reagent MgR.sub.2, wherein X is halogen and R is an aliphatic
group, or active Magnesium is preferably added to convert the
remaining halogen end groups to Grignard groups. Subsequently, for
example to give an alkyl end group an excess of an
.omega.-haloalkane is added which will couple to the Grignard.
Alternatively, to give a proton end group the polymerisation is
quenched into a non-solvent such as an alcohol.
[0051] To provide reactive functional end groups, like for example
hydroxyl or amine groups or protected versions thereof, the halogen
end groups are for example reacted with a Grignard reagent R'MgX,
wherein R' is such a reactive functional group or protected
reactive functional group.
[0052] Instead of a Grignard reagent it is also possible to carry
out endcapping using an organo lithium reagent, followed by
addition of an .omega.-haloalkane.
[0053] It is also possible to replace H end groups by reactive
functional groups by using e.g. the methods described in U.S. Pat.
No. 6,602,974, such as a Vilsmeier reaction to introduce aldehyde
groups followed by reduction with metal hydrides to form hydroxyl
groups.
[0054] If the polymer has been fully worked up prior to endcapping,
it is preferred to dissolve the polymer in a good solvent for
Grignard coupling such as diethyl ether or THF. The solution is
then treated for example with the above mentioned organo Grignard
reagent RMgX or MgR.sub.2 or R'MgX or with a zinc reagent, RZnX,
R'ZnX or ZnR.sub.2, where R and R' are as defined above. A suitable
nickel or palladium catalyst is then added along with the
haloalkane.
[0055] This method of endcapping is also effective for example for
polymers prepared by the McCullough or Rieke route.
[0056] In the case of polymers prepared by the Suzuki or Stille
route, these are preferably endcapped as follows: For the Suzuki
reaction at the end of the polymerisation alkyl termination is
preferably obtained by addition of a 2-boronic-5-alkyl thiophene to
react with the bromine end groups, followed by an excess of a
2-bromo-5-alkyl thiophene to react with the boronic end groups. To
obtain a hydrogen endcapped species, reaction with 2-boronic
thiophene followed by an excess of 2-bromo thiophene is required. A
similar process can be employed for the Stille route, but using a
2-trialkyl stannyl reagent, for example 2-trialkyl stannyl-5-alkyl
thiophene, instead of boronic thiophene. Similarly, if the
endcapping is carried out after initial quenching and purification
of the polymer, it is preferred to dissolve the polymer and add a
suitable catalyst.
[0057] Very preferred are endcapped polymers wherein the terminal
groups during or after polymerisation are replaced by H or an alkyl
group (hereinafter also referred to as `polymers endcapped by H or
an alkyl group`).
[0058] Preferably endcapping is carried out before purification of
the polymer. Further preferably endcapping is carried out after
step d) of the process as described above and below. In another
preferred embodiment of the present invention the endcapper is
added during polymerisation to remove the end groups and possibly
control the molecular weight of the polymer.
[0059] Preferably, substantially all molecules in a polymer sample
are endcapped in accordance with this invention, but at least 80%,
preferably at least 90%, most preferably at least 98% are
endcapped.
[0060] By chemical modification of the terminal groups (endcapping)
of the polymers according to the present-invention, it is possible
to prepare novel polymers with different terminal groups. These
polymers are preferably selected of formula I2 5
[0061] wherein n and R.sup.1 have the meanings given in formula I
and II, and X.sup.11 and X.sup.22 are independently of each other
H, halogen, stannate, boronate or an aliphatic, cycloaliphatic or
aromatic group that may also comprise one or more hetero atoms.
[0062] Especially preferably X.sup.11 and X.sup.22 are selected
from H or straight-chain or branched alkyl with 1 to 20, preferably
1 to 12, very preferably 1 to 6 C-atoms, most preferably
straight-chain alkyl or branched alkyl like isopropyl or
tert.butyl. Aromatic groups X.sup.11 and X.sup.22 tend to be bulky
and are less preferred.
[0063] As described above, the end groups X.sup.11 and X.sup.22 are
preferably introduced by reacting the polymer of formula I1 with a
Grignard reagent MgRX, MgR.sub.2 or MgR'X as described above,
wherein R and R' are X.sup.11 or X.sup.22 as defined in formula
I2.
[0064] By introducing suitable functional end groups X.sup.11
and/or X.sup.22 it is possible to prepare block copolymers from the
polymers according to the present invention. For example, if one or
both of the end groups X.sup.11 and X.sup.22 in a polymer of
formula I2 is a reactive group or a protected reactive group, like
for example an optionally protected hydroxy or amine group, they
can be reacted (after removing the protective group) with the end
group of another polymer of formula I2 (e.g. with different groups
R.sup.1 and/or X.sup.11 and/or X.sup.22), or with a polymer of
different structure. If one of X.sup.11 and X.sup.22 is a reactive
group, diblock copolymers can be formed. If both X.sup.11 and
X.sup.22 are reactive groups, a triblock copolymer can be
formed.
[0065] Alternatively a block copolymer can be formed by introducing
reactive or protected reactive groups X.sup.11 and/or X.sup.22,
adding a catalyst and one or monomers, and initiating a new
polymerization reaction starting from the site of the groups
X.sup.11 and/or X.sup.22.
[0066] Suitable functional end groups and methods of their
introduction can be taken from the above disclosure and from prior
art. Details how to prepare block copolymers can be taken e.g. from
U.S. Pat. No. 6,602,974, the entire disclosure of which is
incorporated into this application by reference.
[0067] The process according to the present invention is
exemplarily illustrated in Scheme 1 below, wherein n, R.sup.1,
X.sup.1 and X.sup.2 have the meaning of formula I and II. 6
[0068] If R.sup.1 is a group that is reactive with magnesium under
the process conditions as described above and below, it is
preferably transformed into, or coupled with, a protective group,
in order not to take part in the reactions forming (2) and (3).
Suitable protective groups are known to the expert and described in
the literature, for example in Greene and Greene, "Protective
Groups in Organic Synthesis", John Wiley and Sons, New York
(1981).
[0069] The starting materials and reagents used in the process
according to the present invention are either commercially
available (e.g. from Aldrich) or can be easily synthesized by
methods well known to those skilled in the art.
[0070] In some cases it may be suitable to further purify the
thiophene monomer and the other reagents before using them in the
inventive process. Purification can be carried out by standard
methods known to the expert and described in the literature.
[0071] The process according to the present invention as
exemplarily depicted in Scheme 1 is preferably carried out as
follows:
[0072] In a first step (step a)) a 3-substituted thiophene (1),
preferably 3-substituted 2,5-dihalothiophene, most preferably
3-substituted 2,5-dibromothiophene, like for example
2,5-dibromo-3-alkylthiophene, which is a readily available starting
material, is dissolved in a solvent or a solvent mixture, like for
example diethyl ether.
[0073] The solvent or solvent mixture preferably consists of one or
more polar aprotic solvents, which can be any solvent of this type,
like for example dialkylethers such as diethyl ether, di-n-butyl
ether, di-n-propyl ether, di-isopropyl ether, glycol ethers such as
1,2-dimethoxyethane, ethers with two different alkyl groups such as
tert.-butylmethyl ether, or mixtures thereof, or mixtures of
aromatic or aliphatic solvents such as mixtures of toluene with the
above ethers.
[0074] Preferably the solvent is selected from linear ethers like
diethyl ether, di-n-butyl ether, di-n-propyl ether, di-isopropyl
ether, ethers with two different alkyl groups, 1,2-dimethyoxyethane
or tert.-butylmethyl ether or mixtures thereof, or a mixture of
toluene with one or more of these ethers.
[0075] Especially preferably the solvent is diethyl ether.
[0076] The concentration of the thiophene educt (1) in the solvent
is preferably from 40 to 200 g/l, very preferably from 80 to 130
g/l.
[0077] In a second step (step b)) magnesium is added to the
reaction mixture in an at least molar amount of the thiophene educt
(1), preferably in an excessive amount from more than 1 to 3,
preferably from 1.01 to 2.00, very preferably from 1.02 to 1.50,
most preferably from 1.02 to 1.20 times the molar amount of the
thiophene educt.
[0078] The Grignard reaction is then started for example by heating
the reaction mixture to reflux or by adding a suitable starting
agent such as Br.sub.2, I.sub.2, DIBAH (diisobutylaluminium
hydride) or others, or by other methods of activating the magnesium
surface. The Grignard reaction is then allowed to proceed,
optionally under agitating and/or heating the reaction mixture, for
a sufficient period of time to give the intermediate (2).
[0079] In an optional next step (step c)), the non-reacted
magnesium is then removed from the reaction mixture e.g. by
filtration. Preferably the magnesium is removed.
[0080] In the next step (step d)), a suitable catalyst is added to
the reaction mixture in an effective amount to initiate the
polymerisation via a Grignard metathesis reaction. Usually the
catalyst is reactive enough to start the polymerisation without
other means, however in practice the mixture is typically stirred
while adding the catalyst.
[0081] Alternatively, it is possible to add the reaction mixture to
the catalyst.
[0082] The catalyst in step d) can be any catalyst that is suitable
for a reaction involving organometallic reagents, including for
example Ni, Pd or other transition metal catalysts. Preferably it
is selected from nickel catalysts, in particular Ni(II) catalysts
like Ni(dppp)Cl.sub.2 (1,3-diphenylphosphinopropane nickel(II)
chloride) or Ni(dppe)Cl.sub.2 (1,2-bis(diphenylphosphino)ethane
nickel(II) chloride), furthermore e.g. copper catalysts like CuI,
CuBr or Li.sub.2CuCl.sub.4 or Pd catalysts like Pd(PPh.sub.3),
PdCl.sub.2(dppe).
[0083] The catalyst is preferably added in an amount from 0.1 to
5%, preferably 0.5 to 2 mol % of the thiophene educt.
[0084] The polymerisation (Grignard metathesis) reaction is then
allowed to proceed, optionally under agitating and/or heating the
reaction mixture, for a sufficient period of time to give the
polymer (3).
[0085] The process according to the present invention may be run at
any temperature providing a sufficient conversion rate. It is
preferred that the reaction is performed at a temperature between
-5.degree. C. and the solvent's reflux temperature, in particular
at the temperatures as specified above and below. The term "reflux
temperature" includes temperatures at or slightly below the boiling
point of the solvent.
[0086] The selection of a suitable reaction time depends on the
actual rate of the individual reaction. Preferably the reaction
times are as given above and below.
[0087] For the reaction of the thiophene educt with magnesium (step
b)) the reaction temperature is preferably in the range from
10.degree. C. to reflux temperature, most preferably from room
temperature to reflux temperature. The reaction time is from 15 min
to 24 h, preferably from 30 min to 6 h.
[0088] For the polymerisation reaction (step d)) the temperature is
preferably in the range from -5.degree. C. to reflux temperature,
most preferably from room temperature to reflux temperature. The
reaction time is from 15 min to 48 h, preferably from 45 min to 4
h.
[0089] The reactions according to steps b) and d) are optionally
carried out under agitating the reaction mixture, which can be
achieved by known methods.
[0090] Steps a) to d), in particular steps b) and d) are preferably
carried out under a dry and inert atmosphere, e.g. under
nitrogen.
[0091] The reaction products (2) and (3) prepared by the process
according to the present invention may be isolated by usual work-up
and purification with standard procedures well known to those
skilled in the art.
[0092] The intermediate (2) obtained in step b) is directly used in
step d). However, for the purpose of e.g. investigating the
proceeding of the reaction process or analysing the ratio of the
regiochemical intermediates produced it may be suitable to quench
the reaction mixture.
[0093] In the last step (step e)) the polymer (3) is recovered from
the reaction mixture. Preferably the polymer is recovered from the
mixture by quenching the reaction mixture with an alcoholic or
aqueous solution or/and precipitating the polymer.
[0094] The polymer can then be purified by known methods to remove
inorganic impurities as well as monomers and short-chain oligomers,
or may also be used without further purification. Preferably the
polymer is purified. Suitable and preferred purification methods
include solid-phase extraction, liquid-liquid extraction,
precipitation, adsorption and filtration. Preferably a combination
of purification methods is selected to obtain a high-purity product
best suitable for application,
[0095] For example a preferred purification method includes aqueous
quenching, for example with a mixture of chloroform/water, optional
liquid/liquid extraction or distilling off the original solvent,
precipitation into a polar solvent like for example methanol, and
washing with an unpolar solvent like for example heptane.
[0096] Suitable reagents and process conditions for the steps d)
and e) including the reaction of the intermediate (2) to the
polymer (3), can also be taken from McCullough et al., Adv. Mater.,
1999, 11(3), 250-253, EP 1 028 136 and U.S. Pat. No. 6,166,172, the
entire disclosure of these documents being incorporated into this
application by reference.
[0097] An especially preferred embodiment relates to a process
including the following steps
[0098] a) dissolving a thiophene having two groups that are capable
of reacting with magnesium, preferably a thiophene of formula II,
very preferably in an amount of from 40 to 200 g/l, in diethyl
ether,
[0099] b) adding magnesium in 1.02 to 1.20 times the molar amount
of the thiophene, or adding the thiophene solution to the
magnesium, and heating the mixture to reflux to form a
regiochemical Grignard intermediate,
[0100] c) removing the unreacted magnesium from the reaction
mixture,
[0101] d) adding a Ni(II) catalyst, preferably Ni(DPPP)Cl.sub.2 or
Ni(DPPE)Cl.sub.2 to the reaction mixture, or adding the reaction
mixture to the Ni(II) catalyst, and agitating the resulting
mixture, preferably under reflux, to form a polymer, and
[0102] e) recovering the polymer from the mixture.
[0103] The intermediate (2) is usually obtained as a mixture of
regiochemical isomers (2a) and (2b), and may also include a,
typically small, amount of the double-Grignard product (2c), as
shown below, wherein X.sup.1, X.sup.2 and R.sup.1 have the meanings
of formula I and I1 7
[0104] The ratio of these intermediates is depending for example on
the molar excess of Magnesium, the solvent, temperature and
reaction time.
[0105] For example, if the reaction is carried out according to the
especially preferred embodiment described above, the intermediates
2a, 2b and 2c can be obtained in a ratio of 85/5/10.
[0106] Depending on the processing conditions, like for example the
solvent and the amount of magnesium, the ratio of isomer
intermediates 2a/2b/2c can be varied. A preferred process includes
isomer intermediate ratios 2a/2b/2c of 80-90/2-20/0-20.
[0107] The polymers according to the present invention are
especially preferably regioregular HT-poly-(3-substituted)
thiophenes. The regioregularity (=head-to-tail couplings divided by
the total couplings, and expressed as a percentage), in these
polymers is preferably at least 85%, in particular 90% or more,
very preferably 95% or more, most preferably from 98 to 100%.
[0108] Polymers of formula I, I1 and I2 having a high percentage of
HT-couplings accordingly have a corresponding high number of HT
dyads or HT-HT-triads formula Ia/b, I1a/b and I2a/b shown below.
8
[0109] wherein R.sup.1, X.sup.1, X.sup.2, X.sup.11, X.sup.22 have
the meanings given above.
[0110] Regioregular poly-(3-substituted) thiophenes are
advantageous as they show strong interchain pi-pi-stacking
interactions and a high degree of crystallinity, making them
effective charge transport materials with high carrier mobilities,
as described for example in U.S. Pat. No. 6,166,172.
[0111] The polymers according to the present invention preferably
have a degree of polymerisation (or number n of recurring units)
from 2 to 5,000, in particular from 10 to 5,000 or from 110 to
5,000, very preferably from 50 to 1,000, most preferably from above
100 to 1,000.
[0112] Further preferred are polymers having a molecular weight
from 5,000 to 300,000, in particular from 10,000 to 100,000,
preferably from 15,000 to 100,000, very preferably from 20,000 to
100,000.
[0113] R.sup.1 in formula I, I1 and II is preferably an organic
group, preferably a non-reactive or protected reactive organic
group, which has preferably 5 or more C-atoms.
[0114] Especially preferably R.sup.1 is straight chain, branched or
cyclic alkyl with 1 or more, preferably 5 or more, very preferably
1 to 20 C-atoms, which may be unsubstituted, mono- or
poly-substituted by F, Cl, Br, I or CN, it being also possible for
one or more non-adjacent CH.sub.2 groups to be replaced, in each
case independently from one another, by --O--, --S--, --NH--,
--NR.sup.0--, --SiR.sup.0R.sup.00--, --CO--, --COO--, --OCO--,
--OCO--O--, --SO.sub.2--, --S--CO--, --CO--S--,
--CY.sup.1.dbd.CY.sup.2-- or --C.ident.C-- in such a manner that O
and/or S atoms are not linked directly to one another, optionally
substituted aryl or heteroaryl preferably having 1 to 30 C-atoms,
or P-Sp, with
[0115] R.sup.0 and R.sup.00 being independently of each other H or
alkyl with 1 to 12 C-atoms,
[0116] Y.sup.1 and Y.sup.2 being independently of each other H, F,
Cl or CN,
[0117] P being a polymerisable or reactive group which is
optionally protected, and
[0118] Sp being a spacer group or a single bond.
[0119] X.sup.1 and X.sup.2 in formula I1 and II are preferably
independently of each other selected from halogen, very preferably
Cl or Br, most preferably Br.
[0120] X.sup.11 and X.sup.22 in formula I2 are preferably
independently of each other selected from H, halogen, B(OR')(OR")
or SnR.sup.0R.sup.00R.sup.000 or straight chain, branched or cyclic
alkyl with 1 to 20 C-atoms, which may be unsubstituted, mono- or
poly-substituted by F, Cl, Br, I, --CN and/or --OH, it being also
possible for one or more non-adjacent CH.sub.2 groups to be
replaced, in each case independently from one another, by --O--,
--S--, --NH--, --NR.sup.0--, --SiR.sup.0R.sup.00--, --CO--,
--COO--, --OCO--, --OCO--O--, --S--CO--, --CO--S--,
--CY.sup.1.dbd.CY.sup.2-- or --C.ident.C-- in such a manner that O
and/or S atoms are not linked directly to one another, optionally
substituted aryl or heteroaryl, or P-Sp, with R.sup.0, R.sup.00,
Y.sup.1, Y.sup.2, P and Sp having the meanings given above,
[0121] R.sup.000 being H or alkyl with 1 to 12 C-atoms, and
[0122] R' and R" being independently of each other H or alkyl with
1 to 12 C-atoms, or OR' and OR" together with the boron atom may
also form a cyclic group having 2 to 10 C atoms.
[0123] Especially preferred are polymers and compounds of formula
I, II, I1 and I2 wherein
[0124] R.sup.1 is an organic group, preferably an alkyl group with
5 or more C-atoms,
[0125] R.sup.1 is a straight-chain alkyl group with 1 to 12,
preferably 5 to 12 C-atoms,
[0126] R.sup.1 is n-hexyl,
[0127] R.sup.1 is selected from C.sub.1-C.sub.20-alkyl that is
optionally substituted with one or more fluorine atoms,
C.sub.1-C.sub.20-alkenyl, C.sub.1-C.sub.20-alkynyl,
C.sub.1-C.sub.20-alkoxy, C.sub.1-C.sub.20-thioalkyl,
C.sub.1-C.sub.20-silyl, C.sub.1-C.sub.20-ester,
C.sub.1-C.sub.20-amino, C.sub.1-C.sub.20-fluoroal- kyl, optionally
substituted aryl or heteroaryl, or P-Sp-, in particular
C.sub.1-C.sub.20-alkyl or C.sub.1-C.sub.20-fluoroalkyl, preferably
straight-chain groups,
[0128] R.sup.1 is selected from alkyl that is optionally
substituted with one or more fluorine atoms, alkenyl, alkynyl,
alkoxy, thioalkyl or fluoroalkyl, all of which are straight-chain
and have 1 to 12, preferably 5 to 12 C-atoms,
[0129] R.sup.1 is selected from pentyl., hexyl, heptyl, octyl,
nonyl, decyl, undecyl or dodecyl,
[0130] X.sup.1 and X.sup.2 have the same meaning,
[0131] X.sup.1 and X.sup.2 denote Br,
[0132] X.sup.11 and X.sup.22 have the same meaning,
[0133] X.sup.11 and X.sup.22 denote H,
[0134] X.sup.11 and X.sup.22 are selected from alkyl that is
optionally substituted with one or more fluorine atoms, alkenyl,
alkynyl, alkoxy, thioalkyl, silyl, ester, amino or fluoroalkyl, all
of these groups being straight-chain or branched and having 1 to
20, preferably 1 to 12, most preferably 1 to 6 C atoms, or
optionally substituted aryl or heteroaryl, or P-Sp as defined
above, in particular straight-chain or branched
C.sub.1-C.sub.6-alkyl, most preferably isopropyl, tert.butyl, or
2-methylbutyl,
[0135] n is an integer from 2 to 5000, in particular 50 to
1000.
[0136] If in formula I, II, I1 and I2 R.sup.1 is an alkyl or alkoxy
radical, i.e. where the terminal CH.sub.2 group is replaced by
--O--, this may be straight-chain or branched. It is preferably
straight-chain, has 2 to 8 carbon atoms and accordingly is
preferably ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl,
ethoxy, propoxy, butoxy, pentoxy, hexyloxy, heptoxy, or octoxy,
furthermore methyl, nonyl, decyl, undecyl, dodecyl, tridecyl,
tetradecyl, pentadecyl, nonoxy, decoxy, undecoxy, dodecoxy,
tridecoxy or tetradecoxy, for example. Especially preferred are
n-hexyl and n-dodecyl.
[0137] If in formula I, II, I1 and I2 R.sup.1 is oxaalkyl, i.e.
where one CH.sub.2 group is replaced by --O--, is preferably
straight-chain 2-oxapropyl (=methoxymethyl), 2-(=ethoxymethyl) or
3-oxabutyl (=2-methoxyethyl), 2-, 3-, or 4-oxapentyl, 2-, 3-, 4-,
or 5-oxahexyl, 2-, 3-, 4-, 5-, or 6-oxaheptyl, 2-, 3-, 4-, 5-, 6-
or 7-oxaoctyl, 2-, 3-, 4-, 5-, 6-, 7- or 8-oxanonyl or 2-, 3-, 4-,
5-, 6-, 7-, 8- or 9-oxadecyl, for example. If in formula I, II and
I1 R.sup.1 is thioalkyl, i.e where one CH.sub.2 group is replaced
by --S--, is preferably straight-chain thiomethyl (--SCH.sub.3),
1-thioethyl (--SCH.sub.2CH.sub.3), 1-thiopropyl
(=--SCH.sub.2CH.sub.2CH.sub.3), 1-(thiobutyl), 1-(thiopentyl),
1-(thiohexyl), 1-(thioheptyl), 1-(thiooctyl), 1-(thiononyl),
1-(thiodecyl), 1-(thioundecyl) or 1-(thiododecyl), wherein
preferably the CH.sub.2 group adjacent to the sp.sup.2 hybridised
vinyl carbon atom is replaced.
[0138] If in formula I, II, I1 and I2 R.sup.1 is fluoroalkyl, it is
preferably straight-chain perfluoroalkyl C.sub.iF.sub.2i+1, wherein
i is an integer from 1 to 15, in particular CF.sub.3,
C.sub.2F.sub.5, C.sub.3F.sub.7, C.sub.4F.sub.9, C.sub.5F.sub.11,
C.sub.6F.sub.13, C.sub.7F.sub.15 or C.sub.8F.sub.17, very
preferably C.sub.6F.sub.13.
[0139] Halogen is preferably F, Br or Cl.
[0140] --CY.sup.1.dbd.CY.sup.2-- is preferably --CH.dbd.CH--,
--CF.dbd.CF-- or --CH.dbd.C(CN)--.
[0141] Aryl and heteroaryl preferably denote a mono-, bi- or
tricyclic aromatic or heteroaromatic group with up to 25 C atoms
that may also comprise condensed rings and is optionally
substituted with one or more groups L, wherein L is halogen or an
alkyl, alkoxy, alkylcarbonyl or alkoxycarbonyl group with 1 to 12 C
atoms, wherein one or more H atoms may be replaced by F or Cl.
[0142] Especially preferred aryl and heteroaryl groups are phenyl
in which, in addition, one or more CH groups may be replaced by N,
naphthalene, thiophene, thienothiophene, dithienothiophene, alkyl
fluorene and oxazole, all of which can be unsubstituted, mono- or
polysubstituted with L as defined above.
[0143] Another preferred embodiment of the present invention
relates to polythiophenes that are substituted in 3-position with a
polymerisable or reactive group, which is optionally protected
during the process of forming the polythiophene. Particular
preferred polymers of this type are those of formula I, I1 or I2
wherein R.sup.1 denotes P-Sp. These polymers are particularly
useful as semiconductors or charge transport materials, as they can
be crosslinked via the groups P, for example by polymerisation in
situ, during or after processing the polymer into a thin film for a
semiconductor component, to yield crosslinked polymer films with
high charge carrier mobility and high thermal, mechanical and
chemical stability.
[0144] The polymerisable or reactive group P is preferably selected
from 9
[0145] with W.sup.1 being H, Cl, CN, phenyl or alkyl with 1 to 5
C-atoms, in particular H, Cl or CH.sub.3, W.sup.2 and W.sup.3 being
independently of each other H or alkyl with 1 to 5 C-atoms, in
particular methyl, ethyl or n-propyl, W.sup.4, W.sup.5 and W.sup.6
being independently of each other Cl, oxaalkyl or oxacarbonylalkyl
with 1 to 5 C-atoms, Phe being 1,4-phenylene and k.sub.1 and
k.sub.2 being independently of each other 0 or 1, or a protected
derivative of these groups which is non-reactive with magnesium
under the conditions described for the process according to the
present invention. Suitable protective groups are known to the
expert and described in the literature, for example in Greene and
Greene, "Protective Groups in Organic Synthesis", John Wiley and
Sons, New York (1981), like for example acetals or ketals.
[0146] Preferably, however, the polymerisable group is added to the
inventive polymers as the last step, after polymerisation.
[0147] Especially preferred groups P are CH.sub.2.dbd.CH--COO--,
CH.sub.2.dbd.C(CH.sub.3)--COO--, CH.sub.2.dbd.CH--,
CH.sub.2.dbd.CH--O--, (CH.sub.2.dbd.CH).sub.2CH--OCO--,
(CH.sub.2.dbd.CH).sub.2CH--O--, and 10
[0148] or protected derivatives thereof.
[0149] Polymerisation of group P can be carried out according to
methods that are known the expert and described in the literature,
for example in D. J. Broer; G. Challa; G. N. Mol, Macromol. Chem,
1991, 192, 59.
[0150] As spacer group Sp all groups can be used that are known for
this purpose to the skilled in the art. The spacer group Sp is
preferably of formula Sp'-X', such that P-Sp- is P-Sp'-X'-,
wherein
[0151] Sp' is alkylene with up to 30 C atoms which is unsubstituted
or mono- or polysubstituted by F, Cl, Br, I or CN, it being also
possible for one or more non-adjacent CH.sub.2 groups to be
replaced, in each case independently from one another, by --O--,
--S--, --NH--, --NR.sup.0--, --SiR.sup.0R.sup.00--, --CO--,
--COO--, --OCO--, --OCO--O--, --S--CO--, --CO--S--, --CH.dbd.CH--
or --C.dbd.C-- in such a manner that O and/or S atoms are not
linked directly to one another,
[0152] X' is --O--, --S--, --CO--, --COO--, --OCO--, --O--COO--,
--CO--NR.sup.0--, --NR.sup.0--CO--, --OCH.sub.2--, --CH.sub.2O--,
--SCH.sub.2--, --CH.sub.2S--, --CF.sub.2O--, --OCF.sub.2--,
--CF.sub.2S--, --SCF.sub.2--, --CF.sub.2CH.sub.2--,
--CH.sub.2CF.sub.2--, --CF.sub.2CF.sub.2--, --CH.dbd.N--,
--N.dbd.CH--, --N.dbd.N--, --CH.dbd.CR.sup.0--,
--CY.sup.1.dbd.CY.sup.2--, --C.ident.C--, --CH.dbd.CH--COO--,
--OCO--CH.dbd.CH-- or a single bond,
[0153] R.sup.0 and R.sup.00 are independently of each other H or
alkyl with 1 to 12 C-atoms, and
[0154] Y.sup.1 and Y.sup.2 are independently of each other H, F, Cl
or CN.
[0155] X' is preferably --O--, --S--, --OCH.sub.2--, --CH.sub.2O--,
--SCH.sub.2--, --CH.sub.2S--, --CF.sub.2O--, --OCF.sub.2--,
--CF.sub.2S--, --SCF.sub.2--, --CH.sub.2CH.sub.2--,
--CF.sub.2CH.sub.2--, --CH.sub.2CF.sub.2--, --CF.sub.2CF.sub.2--,
--CH.dbd.N--, --N.dbd.CH--, --N.dbd.N--, --CH.dbd.CR.sup.0--,
--CY.sup.1.dbd.CY.sup.2--, --C.ident.C-- or a single bond, in
particular --O--, --S--, --C.ident.C--, --CY.sup.1.dbd.CY.sup.2--
or a single bond. In another preferred embodiment X' is a group
that is able to form a conjugated system, such as --C.ident.C-- or
--CY.sup.1.dbd.CY.sup.2--, or a single bond. Typical groups Sp'
are, for example, --(CH.sub.2).sub.p--,
--(CH.sub.2CH.sub.2O).sub.q--CH.sub.2CH.sub.2--,
--CH.sub.2CH.sub.2--S--C- H.sub.2CH.sub.2-- or
--CH.sub.2CH.sub.2--NH--CH.sub.2CH.sub.2-- or
--(SiR.sup.0R.sup.00--O).sub.p--, with p being an integer from 2 to
12, q being an integer from 1 to 3 and R.sup.0 and R.sup.00 having
the meanings given above.
[0156] Preferred groups Sp' are ethylene, propylene, butylene,
pentylene, hexylene, heptylene, octylene, nonylene, decylene,
undecylene, dodecylene, octadecylene, ethyleneoxyethylene,
methyleneoxybutylene, ethylene-thioethylene,
ethylene-N-methyl-iminoethylene, 1-methylalkylene, ethenylene,
propenylene and butenylene for example.
[0157] The polymers of the present invention are useful as optical,
electronic and semiconductor materials, in particular as charge
transport materials in field effect transistors (FETs), e.g., as
components of integrated circuitry, ID tags or TFT applications.
Alternatively, they may be used in organic light emitting diodes
(OLEDs) in electroluminescent display applications or as backlight
of, e.g., liquid crystal displays, as photovoltaics or sensor
materials, for electrophotographic recording, and for other
semiconductor applications.
[0158] The polymers according to the present invention show
especially advantageous solubility properties which allow
production processes using solutions of these compounds. Thus
films, including layers and coatings, may be generated by low cost
production techniques, e.g., spin coating. Suitable solvents or
solvent mixtures comprise alkanes and/or aromatics, especially
their fluorinated or chlorinated derivatives.
[0159] The polymers of the present invention are especially useful
as charge transport materials in FETs. Such FETs, where an organic
semiconductive material is arranged as a film between a
gate-dielectric and a drain and a source electrode, are generally
known, e.g., from U.S. Pat. No. 5,892,244, WO 00/79617, U.S. Pat.
No. 5,998,804, and from the references cited in the background and
prior art chapter and listed below. Due to the advantages, like low
cost production using the solubility properties of the compounds
according to the invention and thus the processibility of large
surfaces, preferred applications of these FETs are such as
integrated circuitry, TFT-displays and security applications.
[0160] In security applications, field effect transistors and other
devices with semiconductive materials, like transistors or diodes,
may be used for ID tags or security markings to authenticate and
prevent counterfeiting of documents of value like banknotes, credit
cards or ID cards, national ID documents, licenses or any product
with money value, like stamps, tickets, shares, cheques etc.
[0161] Alternatively, the polymers according to the invention may
be used in organic light emitting devices or diodes (OLEDs), e.g.,
in display applications or as backlight of e.g. liquid crystal
displays. Common OLEDs are realized using multilayer structures. An
emission layer is generally sandwiched between one or more
electron-transport and/or hole-transport layers. By applying an
electric voltage electrons and holes as charge carriers move
towards the emission layer where their recombination leads to the
excitation and hence luminescence of the lumophor units contained
in the emission layer. The inventive compounds, materials and films
may be employed in one or more of the charge transport layers
and/or in the emission layer, corresponding to their electrical
and/or optical properties. Furthermore their use within the
emission layer is especially advantageous, if the polymers
according to the invention show electroluminescent properties
themselves or comprise electroluminescent groups or compounds. The
selection, characterization as well as the processing of suitable
monomeric, oligomeric and polymeric compounds or materials for the
use in OLEDs is generally known by a person skilled in the art,
see, e.g., Meerholz, Synthetic Materials, 111-112, 2000, 31-34,
Alcala, J. Appl. Phys., 88, 2000, 7124-7128 and the literature
cited therein.
[0162] According to another use, the polymers according to the
present invention, especially those which show photoluminescent
properties, may be employed as materials of light sources, e.g., of
display devices such as described in EP 0 889 350 A1 or by C. Weder
et al., Science, 279, 1998, 835-837.
[0163] A further aspect of the invention relates to both the
oxidised and reduced form of the polymers according to this
invention. Either loss or gain of electrons results in formation of
a highly delocalised ionic form, which is of high conductivity.
This can occur on exposure to common dopants. Suitable dopants and
methods of doping are known to those skilled in the art, e.g., from
EP 0528 662, U.S. Pat. No. 5,198,153 or WO 96/21659.
[0164] The doping process typically implies treatment of the
semiconductor material with an oxidating or reducing agent in a
redox reaction to form delocalised ionic centres in the material,
with the corresponding counterions derived from the applied
dopants. Suitable doping methods comprise for example exposure to a
doping vapor in the atmospheric pressure or at a reduced pressure,
electrochemical doping in a solution containing a dopant, bringing
a dopant into contact with the semiconductor material to be
thermally diffused, and ion-implantantion of the dopant into the
semiconductor material.
[0165] When electrons are used as carriers, suitable dopants are
for example halogens (e.g., I.sub.2, Cl.sub.2, Br.sub.2, ICl,
ICl.sub.3, IBr and IF), Lewis acids (e.g., PF.sub.5, AsF.sub.5,
SbF.sub.5, BF.sub.3, BCl.sub.3, SbCl.sub.5, BBr.sub.3 and
SO.sub.3), protonic acids, organic acids, or amino acids (e.g., HF,
HCl, HNO.sub.3, H.sub.2SO.sub.4, HClO.sub.4, FSO.sub.3H and
ClSO.sub.3H), transition metal compounds (e.g., FeCl.sub.3, FeOCl,
Fe(ClO.sub.4).sub.3, Fe(4-CH.sub.3C.sub.6H.sub.- 4SO.sub.3).sub.3,
TiCl.sub.4, ZrCl.sub.4, HfCl.sub.4, NbF.sub.5, NbCl.sub.5,
TaCl.sub.5, MoF.sub.5, MoCl.sub.5, WF.sub.5, WCl.sub.6, UF.sub.6
and LnCl.sub.3 (wherein Ln is a lanthanoid), anions (e.g.,
Cl.sup.-, Br.sup.-, I.sup.-, I.sub.3.sup.-, HSO.sub.4.sup.-,
SO.sub.4.sup.2-, NO.sub.3.sup.-, ClO.sub.4.sup.-, BF.sub.4.sup.-,
PF.sub.6.sup.-, AsF.sub.6.sup.-, SbF.sub.6.sup.-, FeCl.sub.4.sup.-,
Fe(CN).sub.6.sup.3-, and anions of various sulfonic acids, such as
aryl-SO.sub.3.sup.-). When holes are used as carriers, examples of
dopants are cations (e.g., H.sup.+, Li.sup.+, Na.sup.+, K.sup.+,
Rb.sup.+ and Cs.sup.+), alkali metals (e.g., Li, Na, K, Rb, and
Cs), alkaline-earth metals (e.g., Ca, Sr, and Ba), O.sub.2,
XeOF.sub.4, (NO.sub.2.sup.+)(SbF.sub.6.sup.-),
(NO.sub.2.sup.+)(SbCl.sub.6.sup.-),
(NO.sub.2.sup.+)(BF.sub.4.sup.-), AgClO.sub.4, H.sub.2IrCl.sub.6,
La(NO.sub.3).sub.3 6H.sub.2O, FSO.sub.2OOSO.sub.2F, Eu,
acetylcholine, R.sub.4N.sup.+, (R is an alkyl group),
R.sub.4P.sup.+ (R is an alkyl group), R.sub.6As.sup.+ (R is an
alkyl group), and R.sub.3S.sup.+ (R is an alkyl group).
[0166] The conducting form of the polymers of the present invention
can be used as an organic "metal" in applications, for example, but
not limited to, charge injection layers and ITO planarising layers
in organic light emitting diode applications, films for flat panel
displays and touch screens, antistatic films, printed conductive
substrates, patterns or tracts in electronic applications such as
printed circuit boards and condensers.
[0167] According to another use the polymers according to the
present invention, especially their water-soluble derivatives (for
example with polar or ionic side groups) or ionically doped forms,
can be employed as chemical sensors or materials for detecting and
discriminating DNA sequences. Such uses are described for example
in L. Chen, D. W. McBranch, H. Wang, R. Helgeson, F. Wudl and D. G.
Whitten, Proc. Natl. Acad. Sci. U.S.A. 1999, 96, 12287; D. Wang, X.
Gong, P. S. Heeger, F. Rininsland, G. C. Bazan and A. J. Heeger,
Proc. Natl. Acad. Sci. U.S.A. 2002, 99, 49; N. DiCesare, M. R.
Pinot, K. S. Schanze and J. R. Lakowicz, Langmuir 2002, 18, 7785;
D. T. McQuade, A. E. Pullen, T. M. Swager, Chem. Rev. 2000, 100,
2537.
[0168] The examples below serve to illustrate the invention without
limiting it. In the foregoing and the following, all temperatures
are given in degrees Celsius, and all percentages are by weight,
unless stated otherwise.
[0169] Without further elaboration, it is believed that one skilled
in the art can, using the preceding description, utilize the
present invention to its fullest extent. The following preferred
specific embodiments are, therefore, to be construed as merely
illustrative, and not limitative of the remainder of the disclosure
in any way whatsoever.
[0170] In the foregoing and in the following examples, all
temperatures are set forth uncorrected in degrees Celsius and, all
parts and percentages are by weight, unless otherwise
indicated.
EXAMPLE 1
[0171] a) Polymerisation:
[0172] 9.7 g of 2,5-dibromo-3-hexylthiophene are dissolved in 100
ml diethylether. To 10% of this prepared solution 0.8 g magnesium
are added and heated to reflux. The Grignard reaction is started by
adding one drop of bromine. The rest (90%) of the prepared solution
is added to the reaction mixture during 30 minutes and refluxed for
further 2 hours. Then the excess magnesium is filtered off, the
reaction cooled down to 0.degree. C. and 0.2 g of Ni(dppp)Cl.sub.2
are added to start the polymerisation, and the reaction heated to
reflux.
[0173] b) Work-Up and Purification:
[0174] After 2 more hours of refluxing, 4 ml of isopropylmagnesium
chloride (2 mol/l in diethyl ether) is added for H-endcapping.
[0175] After a reaction time of 2 hours the endcapping is finished
and the reaction mixture is quenched with aqueous methanol.
Extracting the product from the aqueous phase with chloroform and
precipitating it into methanol gives the crude polymer which is
further purified by Soxhlet extractions with methanol and heptane.
Thus, 2.5 g (50%) of pure poly-3-hexylthiophene (.sup.1H-NMR
regioregularity>95%) are obtained. The molecular weight
determined by GPC is M.sub.n=12,600, M.sub.w=21,700, the
polydispersity is 1.7.
COMPARISON EXAMPLE 1
Diiodo Instead of Dibromo Monomer
[0176] Example 1 is repeated but with using
2,5-diiodo-3-hexylthiophene instead of 2,5-dibromo-3-hexylthiophene
in the same molar amounts. However the mixture of Grignard
intermediates precipitates and cannot be polymerised. Changing the
concentration keeps the intermediate products in solution but after
polymerisation an oily product is obtained which cannot be
precipitated from methanol and is soluble in hot heptane,
indicating a low molecular weight. Regioregularity is only around
70%.
COMPARISON EXAMPLE 2
THF Instead of Linear Ether as Solvent
[0177] Example 1 is repeated but with using THF instead of diethyl
ether as solvent. As a result a low molecular weight product is
obtained that is soluble in hot heptane and has a regioregularity
only around 90%.
EXAMPLE 2
Endcapping (replacing Br by H)
[0178] Poly-3-hexylthiophene is prepared as described in example
1a). At the end of the polymerisation reaction a portion of the
reaction mixture is end capped with H as described in example 1 b)
and a portion is worked up without endcapping by immediate
precipitation prior to the addition of the Grignard reagent.
Analysis by MALDI-TOF mass spectroscopy (Matrix-Assisted
Laser-Desorption/Ionization Time-Of-Flight, see M. Karas and F.
Hillenkamp, Anal. Chem. 1988, 60, 2299 and J. Liu., R. S. Loewe and
R. D. McCullough, Macromolecules, 1999, 32, 5777) indicate that the
endcapped sample has predominantly H end groups, whereas the
non-end-capped sample has a much higher amount of bromine end
groups.
EXAMPLE 3
Endcapping (Replacing Br by Propyl)
[0179] Poly-3-hexylthiophene is prepared as described in example
1a). At the end of the polymerisation reaction a portion of the
reaction mixture is end capped with an alkyl group by first adding
isopropylmagnesium chloride (2 mol/L in diethylether) and after two
hours adding 1-Bromopropane. The other portion is worked up with
out endcapping. MALDI-TOF MS analysis indicates that the endcapped
sample has predominantly propyl end groups where as the
non-endcapped sample has a much higher amount of bromine end
groups.
EXAMPLE 4
Use of Endcapped Polymer in a Transistor
[0180] Measurements of the maximum current versus voltage are
carried out for Br-terminated and H-endcapped polymers of examples
1 and 2 using substrates and processing conditions as follows.
[0181] Thin-film organic field-effect transistors (OFETs) are
fabricated on highly doped silicon substrates with a thermally
grown silicon oxide (SiO.sub.2) insulating layer, where the
substrate served as a common gate electrode. Transistor
source-drain gold electrodes are photolithographically defined on
the SiO.sub.2 layer. Prior to organic semiconductor deposition, FET
substrates are treated with a silylating agent hexamethyldisilazane
(HMDS). Thin semiconductor films are then deposited by spin-coating
polymer solutions in chloroform on to the FET substrates. The
electrical characterization of the transistor devices, is carried
out in a dry nitrogen atmosphere using computer controlled Agilent
4155C Semiconductor Parameter Analyser.
[0182] The entire disclosures of all applications, patents and
publications, cited herein and of corresponding European
application No. 03017920.4, filed Aug. 6, 2003, and U.S.
Provisional Application Ser. No. 60/493,451, filed Aug. 8, 2003,
are incorporated by reference herein.
[0183] The preceding examples can be repeated with similar success
by substituting the generically or specifically described reactants
and/or operating conditions of this invention for those used in the
preceding examples.
[0184] From the foregoing description, one skilled in the art can
easily ascertain the essential characteristics of this invention
and, without departing from the spirit and scope thereof, can make
various changes and modifications of the invention to adapt it to
various usages and conditions.
[0185] The results are shown in FIGS. 1-3. The effect of the end
groups can be seen in the following ways:
[0186] As can be seen in FIG. 1, maximum current (and hence
mobility) is higher for samples with H end capping with respect to
Br end capping. Samples with H have a higher sub threshold
slope.
[0187] As can be seen in FIGS. 2A and 2B, stability of the samples
to repeated scanning is superior for samples with H end caps (2B)
than for those with bromine end caps (2A).
[0188] Finally, as can be seen in the transitor output scans FIGS.
3A and 3B, at low source-drain voltage H-capped samples (3B) show
good ohmic contact behaviour. The sample with H capping shows
perfect linear behaviour. The Br capped sample (3A) however
displays significant contact resistance as can be seen by the
non-linear behaviour of the current-voltage plot around 0V.
* * * * *